Answer:
m = 54
Step-by-step explanation:
The secant- secant angle 20° is half the difference of the intercepted arcs, that is
 (160 - 2m - 12) = 20° ( multiply both sides by 2 to clear the fraction )
 (160 - 2m - 12) = 20° ( multiply both sides by 2 to clear the fraction )
- 2m + 148 = 40° ( subtract 148 from both sides )
- 2m = - 108 ( divide both sides by - 2 )
m = 54
 
        
                    
             
        
        
        
It will be irrational. The sum of any irrational and rational number will ALWAYS result in a irrational answer. Khan Academy has a video on this if you want to watch it.
        
             
        
        
        
There is no picture attached so not sure what you are talking about
        
                    
             
        
        
        
The point of elimination is to have one variable so example
3x + 2y = 4
7X + 3y = 5
1) Try to find a way to have one variable
7(3x + 2y = 4) ----> 21x + 14y = 28
-3(7x+ 3y = 5) -----> -21x -9y = -15
2) add
0 + 5y = 13
3) solve for the last variable
5y = 13
y = 13/5 = 2 3/5 = 2.8
4) Subsitute the variable to get the other one
3x + 2(2.8) = 4
3x + 5.6 = 4
3x = -1.6
x = 0.533333333 (continue) 
The intersection would be 0.53 with a line above the 3 and 2.8. (0.5333 , 2.8) 
Hope you understand!!